The present invention relates to methods and apparatus for handling particulate, granular and fluidized material, and, more particularly, for unloading large storage bins and receptacles of such material onto a conveyor.
Particulate, granular and fluidized materials, such as grain, soy beans, bark, wood chips, coal and the like, are typically stored in large bins or receptacles. These bins can be static structures measuring over a hundred feet in length and/or width and being several stories high. Particulate matter is, for example, discharged into the top of the bin via a conveyor and allowed to pile up inside. When it is desired to reclaim the particulate matter from the bin, front end loaders or undercutting auger screws are often employed.
Front end loaders have the advantages of requiring minimal capital investment and of simplicity and flexibility of operation. Various different cargo receiving vehicles, such as ships, trains, dump trucks and the like, can be served by a front end loader. However, front end loaders can be dangerous to operate in the environment of particulate matter bins. Undercutting the material pile can, for example, cause the overhang to collapse onto the operator of the front end loader. To decrease such risks in that type of loading arrangement has required greater manpower effort and operational expense.
As an alternative, auger screws have been mounted on rails or tracks at the bin sides so to move back and forth through the pile of material at the base of the bin while rotating about an axis laterally across the width of the bin. Depending upon the width of the bin, either a single screw can extend from one side to the other or two screws are employed which extend from each side to join at the center of the bin floor and are supported at that junction on a meridian track running the longitudinal length of the bin as well. The side tracks are typically mounted in sheds or enclosures formed beside or within the base, and the meridian track is typically mounted beneath a cover or central enclosure of the bin.
Such enclosures serve to contain the motors and drive mechanisms for the screw and keep particulate matter off of the track. Further, motion of the screw directs the particulate matter to one or more conveyors which are also located in one or more of these enclosures. Typically, these conveyors extend the entire length of the bin and outwardly to the vehicle to be loaded. The screws pass through a permanent opening in the enclosures to enter the bins and that same opening is usually employed to permit particulate matter agitated by the screws to leave the bins and fall onto the conveyors. Thus, the conveyors are intended to provide a steady flow of material with a minimum of manpower demands.
However, since the openings of the enclosures extend for far longer that the radial dimensions of the screws, once the screw uncakes the particulate matter adjacent those openings, the flow of matter onto the conveyor can continue for a significant period of time after the screw travels onward. Especially for fluidized material, such as bean meal, this can result in a loss of control of the amount of material applied to the conveyor. As a result, the conveyor can be subject to excessive weight and/or volume loads, and thereby jam or break down. It has been suggested that various special conveyor configurations, such as chain conveyors, can be used to better resist these problems, but such conveyors typically cost more initially and operationally, as well as require a slower material loading flow rate.
Moreover, there are a number of significant design restrictions on such material unloading arrangements that limit the availability of alternative solutions. For example, due to the dusty nature of some materials (and over time the same bins can be used for a variety of materials), it is commonly necessary to make the screw drive devices "explosion proof." Also, since the screws are not always operational, the structure must be capable of sustaining the material weight during non use and start up against a high rotational load. Further, given the large distances between components that must move in unison, proper alignment must be maintained to prevent components from binding.
Other disadvantages of prior auger screw arrangements arise because of the need for side and meridian enclosures. Prior drive mechanisms have been mounted outside of the auger screw, and were often very large due to the large torque needed at screw start up even though lower torques can be used during subsequent operation. As a result, the enclosures also needed to be large, sometimes formed as whole side or meridian rooms of the bin. In addition to requiring greater cost of construction, these rooms detracted from the amount of space available for material storage.
Accordingly, it is an object of the present invention to provide an improved method and apparatus for handling of particulate, granular and/or fluidized material. Other objects include the provision of a method and apparatus which:
1. can be readily retrofit to existing storage bins with a minimum of reconstruction; PA1 2. is reliable and cost efficient both in initial cost and in operational cost; PA1 3. is compact in design so as to minimize spacial requirements within the storage bin; PA1 4. permits greater control over the amount of material applied to the conveyor; PA1 5. is flexible in its application so as not to preclude concurrent or alternative use of front end loaders to reclaim portions of material alternatively of simultaneously; and PA1 6. minimizes the incidences and severity of binding or jamming in operation.
These and other objects of the present invention are attained in a material handling system having a plurality of separately actuatable flow gates disposed between the storage bin and the unloading conveyor which are sequentially opened and closed by a sliding "zipper" cam member to carefully control the amount of material applied to the conveyor. A compact screw drive assembly is mounted within a hollow of the screw at one end and enables the screw to be initially operable at a low speed to provide a higher break away torque when starting the screw and to be then operable at a higher speed and lower torque during constant running of the screw. The drive assembly includes a reversible motor coupled to a speed reducing gear arrangement in the reverse direction such that the motor is run in reverse when starting the screw and then run in forward during constant running of the screw.
Other objects, advantages and novel features of the present invention will now become readily apparent to those skilled in the art from the following drawings and detailed description.